Study Sees No Link Between Antibiotics in Early Pregnancy and Birth Defects

Researchers looked for risk among women prescribed drugs that include azithromycin

SOURCE: University of Montreal, news release, Oct. 29, 2015

FRIDAY, Oct. 30, 2015 (HealthDay News) -- A new Canadian study did not find any association between two common types of antibiotics taken during pregnancy and a higher risk of adverse effects to the baby.

Four out of 10 pregnant women are prescribed antibiotics, with azithromycin and clarithromycin being the most common. They belong to a class of drugs called macrolides.

"With penicillin, macrolides are amongst the most used medications in the general population and in pregnancy. However, debate remained on whether it is the infections or in fact the macrolides used to treat them that put women and their unborn child at greater risk of adverse pregnancy outcomes, including birth defects," said study co-leader Anick Berard, a professor of pharmacy at the University of Montreal.

"We therefore aimed to estimate the risk of major congenital malformations after fetal exposure to the two most commonly used macrolides, and failed to find any," she said in a university news release.

The researchers reviewed more than 135,000 pregnancies in the province of Quebec. About 2 percent of the women were prescribed macrolides during the first trimester of pregnancy. Major birth defects occurred in about 10 percent of the babies.

The researchers did not find an association between use of macrolides and the risk of birth defects, according to the study published Oct. 30 in the journal Pharmacoepidemiology and Drug Safety.

The researchers said previous confusion about the safety of macrolides during pregnancy might stem from several overlooked factors. For example, azithromycin is often used to treat chlamydia infections, which are associated with birth defects, the researchers said.

They added that further studies are needed to confirm the safety of antibiotics less often prescribed to pregnant women.